This document discusses methods for counting blood cells and measuring temperature. It describes the main types of blood cells - red blood cells, white blood cells, and platelets. Methods for counting blood cells include microscopic counting, automatic optical counting, and electrical conductivity counting. The document also discusses systemic and skin temperature measurement and methods like mercury thermometers, electronic thermometers, thermocouples, and thermistors.

1. Blood Cell Counter
Temperature Measurement
S.Vijayakumar
AP, Ramco Institute of Technology

2. Blood Cell Types
 Red blood cells (RBC) / Erythrocytes
 White blood cells (WBC) / Leucocytes
 Blood Platelets / Thrombocytes
Counting Methods:
 Microscopic method
 Automatic Optical method
 Electrical Conductivity method

3. • determination of the number and size of blood
cells per unit volume often provides valuable
information for accurate diagnosis.
• The blood constitutes 5–10% of the total body
weight and in an average adult it amounts to 5–6
litres.
• Blood consists of corpuscles suspended in fluid
called plasma in the proportion of 45 parts of
corpuscles (cells) to 55 parts of plasma

4. • The percentage of cells in the blood is called
the haematocrit value or packed cell volume
(PCV).
• The majority of the corpuscles in blood are
red blood cells (erythrocytes), others being
white blood cells (leucocytes) and platelets
(thrombocytes).

5. Blood Cell Types:
• Erythrocytes (Red Blood Cells):
• RBC is round disks, indented in the centre, with a
diameter of about 8µm.
• In the whole body, there are about 25 billion
erythrocytes and they are constantly being destroyed
and replaced at a rate of about 9000 million per hour.
• The normal red cell lasts approximately 120 days
before it is destroyed.
• The erythrocytes have no nucleus. They are
responsible for carrying oxygen from the lungs to the
tissues and carbon dioxide from the tissues to the
lungs.

6. • Leucocytes (White Blood Cells):
• Its average diameter 10µm.
• Leucocytes are spherical cells having a
nucleus. There are normally 5000–10,000
white cells per cubic mm of blood.
• They live for 7 to 14 days and there is a rapid
turnover, with constant destruction and
replacement.

7. • Leucocytes form the defence mechanism of the
body against infection.
• They are of two main types: the neutrophils and
the lymphocytes.
• Neutrophils ingest bacteria: Neutrophils are
nearly twice as big as the red cells and contain
both a nucleus divided into several lobes and
granules in their protoplasm
• Lymphocytes: Lymphocytes are of the same size
as the red cells but contain a large density
staining nucleus and no granules

8. • Thrombocytes (Platelets):
• Platelets are usually tiny, round, oblong or
irregularly shaped cells of the blood with an
average diameter of approximately 2 - 4μm.
They play an important role in the blood
coagulation process. There are usually
250,000–750,000 platelets in every cubic mm
of blood.

10. METHODS OF CELL COUNTING:
• Microscopic Method
• the microscopic method in which the diluted
sample is visually examined and the cells counted
• drawbacks such as rapid tiring of the person
making the examination and poor reproducibility
of results
• data gathered by this measurement is not directly
suitable for storage or for further processing and
evaluation

11. Automatic Optical Method:
• collecting scattered light from the blood cells
and converting it into electrical pulses for
counting.

12. • Instruments based on this technique take
about 30 s for completing the count.
• An accuracy of 2% is attainable. The
instruments require about 1 ml of blood
sample.

13. Electrical Conductivity Method
• Blood cell counters, operating on the principle
of conductivity change, which occurs each
time a cell passes through an orifice, are
generally known as Coulter Counters.
• The technique is extremely useful for
determining the number and size of the
particles suspended in an electrically
conductive liquid

15. • The number of particles N in a unit volume is
determined from the relation,
• where
• H = factor of dilution
• L = scaling factor of the counter
• V = measured volume
• E = result displayed on the digital display.

16. • In particular, it provides information regarding
– relative cell size,
– relative cell size distribution,
– settings of the threshold level control, and
– Means to check the performance of the
instrument for reliability of counts.

17. Errors in Electronic counters
 Aperture clogging
 Uncertainty of Discriminator Threshold
 Coincidence Error
 Settling Error
 Error in Sample Volume
 Error due to Temperature Variation
 Biological Factors
 Dilution Errors
 Error due to External Disturbance

18. Temperature measurement
• Body temperature is one of the older known
indicators of the general well-being of a
person.
• Two basic types of temperature measurement
can be obtained from the body:
i. Systemic measurement
ii. Skin surface measurement

19. Systemic temperature:
• The temperature of internal regions of the
body.
• Temperature is maintained through a carefully
controlled balance between the heat
generated by the active tissues of the body,
mainly the muscles and the liver and the heat
lost by the body to the environment.

20. • devices placed in mouth, under the armpits,
or in the rectum.
• The normal oral temperature of a healthy
person is 37o C (98.6oF).
• The systemic body temperature can be
measured most accurately at the tympanic
membrane in the ear

21. • The temperature control center for the body is
located deep within the brain.
• Here the temperature of the blood is
monitored and its control functions are
coordinated.

22. Skin or surface temperature:
• Balance is between the heat supplied by blood
circulation in a local area and cooling of that
area by conduction, radiation, convection and
evaporation.
• Skin temperature is a function of the surface
circulation, environmental temperature, air
circulation around the area from which the
measurement is to be taken

23. Measurement of systemic body
temperature:
• Where continuous recording of temperature is
not required, the mercury thermometer is still
the standard method of measurement.
• Devices are inexpensive, easy to use and
sufficiently accurate.
• Electronic thermometers are available as
replacement for mercury thermometers.

24. • Two types of electronic temperature sensing
devices are found in bio-medical applications.
• They are
• i. Thermocouple- a junction of two
dissimilar metals that produces an output
voltage nearly proportional to the
temperature
• ii. Thermistor – a semiconductor element
whose resistance varies with temperature

25. • The resistance of a thermistor at a given
temperature can be determined by the equation:
• Rt1 = Rt0eβ(1/T
1 – 1/T
0
)
• Where Rt1= resistance at temperature T1
• Rt0 = resistance at reference temperature T0
• e = base of natural logarithms
• β = temperature coefficient of the material
• T1 = temperature at which the measurement is
being made
• T0 = reference temperature

26. • The most important characteristics to consider
in selecting a thermistor probe for a specific
biomedical application are the following
• The physical configuration of the thermistor
probe
• Sensitivity
• The absolute temperature range
• Resistance range of the probe

27. Skin temperature measurements
• Although the systemic temperature remains
very constant throughout the body, skin
temperatures can vary several degrees from
one point to another.
• Range is usually from about 30 to 35oC (85 to
95oF).
• flat thermistor probes taped to the skin

28. • Infrared thermometer- a device sensitive to
infrared radiation can accurately read the
surface temperature.
• i. Used to detect breast cancers.
• ii. Used to detect areas of poor
circulation

29. • An extension of this method of skin
temperature measurement is the
thermograph. This device is an infrared
thermometer incorporated into a scanner so
that the entire surface of the body or some
portion of the body is scanned at a slower rate